1. Field of the Invention
This invention relates to terminators for SCSI buses, and more particularly, to monitoring the termination status of terminations on a small computer system interface (SCSI) bus.
2. Description of the Related Art
Buses that comply with the SCSI standard ("SCSI buses") have been generally perceived as being "difficult to use" due to the strict requirements for bus termination set forth in the SCSI standard. For example, for proper termination, SCSI buses must have two, and only two, terminators connected to each end of a particular bus. A device having bus termination capability is said to either be "enabled" or "disabled", according to whether the "status" of the device currently is, or is not set, for bus termination. As is well known to those skilled in the art, a terminator is any device capable of providing termination of the SCSI bus, and which is actually enabled for termination.
It is also known that a passive terminator device may be a terminator merely by being connected to the bus, for example, and that to avoid having the passive terminator device be a terminator, the passive terminator device must be disconnected from the SCSI bus. Also, SCSI bus termination by most computer peripheral devices is not automatic. Rather, such devices require manual insertion or removal of shunt jumpers to enable or disable the device.
As a result of the need to physically disconnect the passive devices to avoid having them be a terminator, and as a result of the need to manually remove the shunt jumpers from the peripheral devices, the termination status of the SCSI bus is too often improper. That is, more than two terminators are set on a single SCSI bus, in which case the bus is said to be "over-terminated", or less than two terminators may be set on the bus, in which case the bus is said to be "under-terminated". Moreover, when the SCSI bus is either under-terminated or over-terminated, the bus will not function properly, and often the user does not know why the bus is not functioning. It may be understood then, that there is an unfilled need for the user to know when the bus is not properly terminated, other than having the bus be inoperative.